Steering control system for a towed axle

ABSTRACT

A trailer includes a chassis having a hitch, an axle having a tractive element rotatably coupled to the chassis, and an actuator coupled to the chassis and positioned to steer the tractive element in response to an input, the input varying based on at least one of a speed, a transmission gear, and a steering mode of a tractor vehicle.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/088,177, filed Nov. 22, 2013, which is incorporated herein byreference in its entirety.

BACKGROUND

The present application relates to sweeper vehicles. In particular, thepresent application relates to the operation of a snow removal apparatusincluding a tow-behind snow removal broom. A snow removal vehicle mayinclude a tractor and a trailer. The tractor may include a snow plow,blower, sweeper, or other apparatus for removing snow. In someinstances, the snow plow, blower, or other apparatus may leave traceamounts of snow behind. Such residual snow may be removed with atow-behind broom mounted on a trailer. It should be understood that thetractor tows the trailer including the tow-behind broom to facilitatesweeping the snow and other material.

Various challenges arise for operators driving the snow removalapparatus. For example, the trailer may not track the path plowed orblown by the snow-removal apparatus on the tractor. Such a lack ofoverlap may leave some areas unswept or may result in damage to thebroom (e.g., due to contact between bristles of the broom and unplowedor unblown snow). While some trailers include axles that are steered tofacilitate tracking, such trailers can be difficult to control in thereverse direction and produce an unfamiliar experience for the operator.

SUMMARY

One embodiment relates to a trailer that includes a chassis having ahitch, an axle having a tractive element rotatably coupled to thechassis, and an actuator coupled to the chassis and positioned to steerthe tractive element in response to an input, the input varying based onat least one of a speed, a transmission gear, and a steering mode of atractor vehicle.

Another embodiment relates to a steering control system that includes anaxle having a tractive element rotatably coupled to a chassis, anactuator positioned to steer the tractive element, and a processingcircuit configured to evaluate at least one of a speed, a transmissiongear, and a steering mode of a tractor vehicle and engage the actuatorsteer the tractive element according to a control strategy that variesbased on at least one of the speed, the transmission gear, and thesteering mode of the tractor vehicle.

Yet another embodiment relates to a method of steering a trailer. Themethod includes identifying an operating state of a tractor vehicle witha processing circuit, steering a tractive element with an actuator whenthe operating state relates to a first mode of operation of the tractorvehicle, and centering the tractive element with the actuator when theoperating state relates to a second mode of operation of the tractorvehicle.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIGS. 1-2 are perspective views of a snow removal vehicle including atractor vehicle and a trailer, according to an exemplary embodiment;

FIG. 3 is a perspective view of a trailer for the snow removal vehicleincluding a broom assembly, according to an exemplary embodiment;

FIGS. 4-8 are partial perspective views of a trailer for a snow removalvehicle having a steering assembly and a locking mechanism, according toan exemplary embodiment;

FIGS. 9-12 are partial perspective views of the hitch portion of atrailer for a snow removal vehicle, according to an exemplaryembodiment;

FIGS. 13A-13F is a schematic diagram of a trailer steering and snowremoval system, according to an exemplary embodiment;

FIG. 14 is a block diagram of a system architecture for steering atrailer, according to an exemplary embodiment;

FIG. 15 is a detailed block diagram of a steering control system forsteering a trailer, according to an exemplary embodiment;

FIG. 16 is a flow chart of a process for steering a trailer, accordingto an exemplary embodiment;

FIG. 17 is a flow chart of a process for locking and unlocking an axleof a trailer, according to an exemplary embodiment; and

FIGS. 18-20 are user interfaces for interacting with a steering controlsystem, according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the application isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

According to the exemplary embodiment shown in FIGS. 1-3, a vehicle,shown as snow removal vehicle 100, includes a tractor 102 and a trailer104. In one embodiment, tractor 102 includes a vehicle specificallydesigned to haul trailer 104. In other embodiments, tractor 102 includesanother type of vehicle (e.g., a pickup truck, a military vehicle, etc.)that includes a hitch. By way of example, the vehicle may be equippedwith a fifth wheel hitch connection, a standard tow hitch including areceiver and a tow ball, or still another coupling. A plurality oftractive elements facilitate movement (e.g., driving, turning, etc.) oftractor 102. In one embodiment, a first set of the tractive elements areused to steer tractor 102, and a second set of tractive elements arecoupled to a vehicle drive train (e.g., including an engine,transmission, etc.) and drive tractor 102. In other embodiments, each ofthe tractive elements drive tractor 102 (e.g., tractor 102 may beall-wheel drive), with a subset of the tractive elements (e.g., thefront wheels) both steering and driving tractor 102. In still otherembodiments, each of the tractive elements both drive and steer tractor102.

As shown in FIGS. 1-2, a snow removal device, shown as plow 106, iscoupled to a front portion of tractor 102. In other embodiments, thesnow removal device includes a blower assembly, a broom, or stillanother device. Plow 106 is configured to plow snow in the path of snowremoval vehicle 100, according to one embodiment. In other embodiments,the snow removal device otherwise interacts with the snow (e.g., blows,sweeps, etc.). According to still other embodiments, tractor 102 doesnot include a snow removal device.

As shown in FIG. 2, trailer 104 includes a broom assembly. The broomassembly may be configured to interface with a material (e.g., snow,debris, etc.) positioned on a surface (e.g., an airport runway, aroadway, a sidewalk, etc.). As shown in FIG. 2, the broom assemblyincludes a broom, shown as broom 108. Broom 108 may include a pluralityof elements (e.g., bristles, flaps, etc.) that are rotated to clearmaterial from the surface. In one embodiment, the broom assemblyincludes a broom controller configured to vary a feature of broom 108(e.g., a position relative to a ground surface, a position relative to aportion of trailer 104, a rotation speed, etc.). The broom controllermay be coupled to various input/output devices (e.g., sensors, ahydraulic system, a user interface, etc.). Such input/output devices maycouple the broom controller to various subsystems of snow removalvehicle 100. While this discussion emphasizes using the vehicle toremove snow, it should be understood that systems and methods disclosedherein may be applied to a vehicle for removing other types of material(e.g., debris). In still other embodiments, tractor 102 and trailer 104are used to perform still other functions (e.g., transport goods, etc.).

As shown in FIG. 2, trailer 104 includes a frame 110 having a hitchportion, shown as hitch 112, and a chassis, shown as chassis 114.According to an exemplary embodiment, hitch 112 couples trailer 104 withtractor 102. It should be understood that trailer 104 may rotaterelative to tractor 102 about hitch 112 (e.g., as tractor 102 turns). Asshown in FIG. 2, trailer 104 includes an axle assembly 116 that includesa pair of tractive elements, shown as wheels 118. According to anexemplary embodiment, wheels 118 rotate relative to chassis 114 and areturned (i.e. steered) according to a steering control strategy. Turningwheels 118 steers trailer 104, thereby reducing the risk of leaving someareas unswept or damaging broom 108 (e.g., due to contact betweenbristles of the broom and unplowed or unblown snow). According to anexemplary embodiment, broom 108 is movably coupled to frame 110 with arotating element (e.g., a slewing ring, etc.).

As shown in FIGS. 1-3, trailer 104 includes a single axle assembly 116having a single pair of wheels 118 coupled to a rear portion of chassis114. According to an alternative embodiment, trailer 104 includes aplurality of axles (e.g., two, three, etc.) each having at least onetractive element (e.g., each having a pair of wheels, each having twopairs of wheels, etc.). According to still another alternativeembodiment, trailer 104 includes an axle otherwise positioned alongchassis 114 (e.g., at the front of chassis 114, in a middle portion ofchassis 114, etc.).

Referring next to FIGS. 4-8, wheels 118 are movably coupled to frame110. By way of example, wheels 118 may rotate about an axis as trailer104 moves (e.g., an axis perpendicular to a direction of travel and avertical axis, an axis perpendicular to a pair of longitudinal framemembers of frame 110 and a vertical axis, etc.). By way of anotherexample, wheels 118 may be turned about still another axis (e.g., akingpin axis, etc.). As shown in FIGS. 4-8, axle assembly 116 includes apair of hubs, shown as hub 120 and hub 122, that couple wheels 118 to aframe member, shown as frame member 117. Hub 120 and hub 122 eachinclude a movable portion that rotates and turns with wheels 118 and afixed portion that is coupled to frame member 117, according to anexemplary embodiment. Frame member 117 may be tubular, may include asolid portion, or may be still otherwise shaped. According to theexemplary embodiment shown in FIGS. 4-8, frame member 117 is coupled toframe 110 of the trailer with a pair of brackets, shown as brackets 119.In other embodiments, frame member 117 may be otherwise coupled to frame110 (e.g., welded to frame 110, directly bolted to frame 110, etc.). Instill other embodiments, axle assembly 116 includes wheels 118 that areotherwise coupled to frame 110 (e.g., directly mounted to a frame railor side plate, coupled with a suspension system, coupled with apneumatic system, coupled with springs or other resilient members,etc.).

According to the embodiment shown in FIGS. 4-8, axle assembly 116includes a steering assembly 130 that turns hub 120 and hub 122 (e.g.,about a kingpin axis) to steer wheels 118. As shown in FIG. 5, steeringassembly 130 includes an actuator, shown as steering cylinder 132,positioned to directly steer hub 120. In one embodiment, steeringcylinder 132 is a hydraulic cylinder. In other embodiments, steeringcylinder 132 is a pneumatic cylinder. In still other embodiments,another type of actuator is positioned to steer hub 120 (e.g., arotational actuator, another type of linear actuator, etc.). A steeringcontrol system may control the operation of steering cylinder 132 inorder to steer wheels 118 based on a steering control strategy.

Steering cylinder 132 may be coupled to frame 110 of snow removalvehicle 100. As shown in FIG. 5, a first end of steering cylinder 132 iscoupled to frame member 117 with a plate, shown as ear 134, and a secondend of steering cylinder 132 is coupled to hub 120 with an arm, shown assteering arm 124. In other embodiments, the first end of steeringcylinder 132 is directly coupled with frame 110 of trailer 104. As shownin FIG. 5, ball joints couple steering cylinder 132 with ear 134 andsteering arm 124. In other embodiments, steering cylinder 132 isotherwise coupled to ear 134 and steering arm 124. Extension andretraction of steering cylinder 132 steers wheels 118. By way ofexample, extension of steering cylinder 132 applies a force laterallyoutward on steering arm 124 that turns hub 120 in a first direction(e.g., turns hub 120 clockwise). By way of further example, retractionof steering cylinder 132 applies a force laterally inward on steeringarm 124 that turns hub 120 in an opposing second direction (e.g., turnshub 120 counterclockwise).

In one embodiment, steering assembly 130 includes a drag link thatcouples the movement of hub 120 and hub 122. Rotatably coupling hub 120and hub 122 may facilitate the steering of trailer 104 with a singleactuator (e.g., a single steering cylinder 132 may steer both hub 120and hub 122). In one embodiment, the drag link is coupled to hub 120 andhub 122 with a pair of arms (e.g., steering arms). The drag link mayextend laterally across a longitudinal axis of trailer 104 (e.g.,parallel to frame member 117). The drag link transfers the steeringforce applied to hub 120 by steering cylinder 132 to hub 122. By way ofexample, extension of steering cylinder 132 may apply a steering forcelaterally outward to rotate hub 120 clockwise, and the drag link maytransfer the steering force to rotate hub 122 clockwise. In oneembodiment, the drag link is coupled to hub 120 forward of an axis ofrotation for wheel 118 (e.g., the kingpin axis), and steering cylinder132 is coupled to hub 120 rearward of the axis of rotation for wheel118. In other embodiments, both the drag link and steering cylinder 132are coupled forward or rearward of the axis of rotation for wheel 118.In other embodiments, axle assembly 116 may include a pair of steeringcylinders 132 to individually steer hub 120 and hub 122.

Referring again to the exemplary embodiment shown in FIGS. 4-8, axleassembly 116 includes a locking mechanism, shown as locking mechanism140. A steering control system may be configured to selectively securewheels 118 by engaging locking mechanism 140. In one embodiment, thesteering control system may receive a user input or other input relatingto a command to secure wheels 118. By way of example, a user command tosecure the orientation of wheels 118 may be provided to a processingcircuit (e.g., after wheels 118 are centered, etc.).

According to the embodiment shown in FIGS. 4-8, locking mechanism 140includes a first plate, shown as support plate 142, that couples anactuator, shown as locking cylinder 144, to hub 120. Support plate 142and locking cylinder 144 turn with hub 120 relative to a second plate,shown as locking plate 146. Locking plate 146 remains stationary assteering cylinder 132 turns hub 120.

In one embodiment, locking cylinder 144 includes a locking pin that ismoveable between an extended position and a retracted position. With thelocking pin in the retracted position, support plate 142 and lockingcylinder 144 are movable, and wheel 118 may be steered. In oneembodiment, locking plate 146 defines an aperture configured to receivean end of the locking pin. Locking cylinder 144 may move the locking pininto the extended position, where an end of the locking pin interfaceswith the aperture within locking plate 146 to secure wheel 118. Inanother embodiment, locking cylinder 144 includes a resilient member(e.g., a spring) positioned to bias the locking pin into the extendedposition. Pneumatic pressure may overcome the spring force to retractthe locking pin, thereby allowing wheel 118 to be steered.

In one embodiment, wheel 118 may be selectively secured. By way ofexample, wheel 118 may be secured in a straight-ahead orientation. Theaperture in locking plate 146 may be positioned to facilitate securingwheel 118 in only the straight-ahead orientation. With wheels 118turned, the locking pin of locking cylinder 144 may be offset from theaperture within locking plate 146. Rotation of wheels 118 into astraight-ahead orientation may align the locking pin with the aperturewithin locking plate 146. With wheels 118 in a straight-aheadorientation, the locking pin may be extended into the aperture withinlocking plate 146 (e.g., with the application of pneumatic pressure, dueto a biasing force from an air-released spring, etc.), thereby securingwheels 118. In other embodiments, locking mechanism 140 otherwiseselectively secures wheels 118.

In still other embodiments, locking cylinder 144 and support plate 142may remain stationary as steering cylinder 132 turns hub 120. As shownin FIGS. 4-8, locking mechanism 140 is coupled to frame member 117 ofaxle assembly 116. In other embodiments, locking mechanism 140 isdirectly coupled to frame 110 of trailer 104. As shown in FIGS. 4-8,axle assembly 116 includes a single locking mechanism 140. By way ofexample, a drag link may couple the movements of hub 120 and hub 122such that a locking mechanism 140 that secures hub 120 also secures hub122. In other embodiments, axle assembly 116 includes a pair of lockingmechanisms 140 to individually secure the positions of hub 120 and hub122.

Referring still to FIGS. 4-8, axle assembly 116 includes a sensor, shownas sensor 136. Sensor 136 may facilitate determining the position of oneor more components (e.g., steering cylinder 132, hub 120, hub 122,etc.). As shown in FIG. 5, sensor 136 is a linear position sensor. Inother embodiments, sensor 136 is another type of sensor (e.g., arotational position sensor, etc.). As shown in FIGS. 4-8, sensor 136 isintegrated within steering cylinder 132. Sensor 136 may detect theposition of steering cylinder 132 (e.g., the position of a movable rodrelative to a cylinder, etc.) and provide a sensor signal relating tothe position thereof to a remote processing circuit of snow removalvehicle 100. The sensor signal may be used to determine a currentposition of at least one of steering cylinder 132, hub 120, hub 122, andtrailer 104. Sensor 136 may be coupled to steering cylinder 132 suchthat the particular location of sensor 136 is dependent upon the currentposition and actuation of steering cylinder 132. The position ofsteering cylinder 132 may be measured in relation to any reference pointon frame 110, snow removal vehicle 100, or any other reference point. Inone embodiment, the remote processing circuit uses the sensor signals toevaluate the position of at least one of steering cylinder 132, hub 120,and hub 122 and sends a command signal to locking mechanism 140 when hub120 and hub 122 are positioned in a straight-ahead orientation (e.g., toexhaust a pneumatic pressure opposing a biasing spring, to directlyinsert the locking pin into the aperture, etc.).

Referring next to FIGS. 9-12, frame 110 includes a hitch 112 and achassis 114. A connecting assembly 115 couples hitch 112 with chassis114. As shown in FIGS. 9-12, connecting assembly 115 includes aplurality of tubular frame members and a pair of actuators. In oneembodiment, the actuators may be extended to elevate chassis 114 orretracted to lower chassis 114. As shown in FIG. 10, hitch 112 includesa hitch stud 113 configured to couple frame 110 to the tractor of thesnow removal vehicle. By way of example, forward pulling forces andrearward pushing forces, among other forces, may be transferred from thetractor to frame 110 through hitch stud 113.

As shown in FIGS. 11-12, a hitch angle sensor 150 is coupled to hitch112. According to the embodiment shown in FIG. 11, hitch angle sensor150 is positioned within an enclosed box section of hitch 112. In otherembodiments, hitch angle sensor 150 is otherwise coupled to hitch 112.Hitch angle sensor 150 is configured to provide sensor signals relatingto the hitch angle of the trailer relative to the tractor, according toan exemplary embodiment. The hitch angle indicates a position of thetrailer behind the tractor. The hitch angle may be an angle measuredfrom any reference on hitch 112, frame 110, or snow removal vehicle 100.Hitch angle sensor 150 may provide a sensor input relating to the hitchangle to a remote processing circuit of snow removal vehicle 100. Thesensor input may be used to determine a target position for a componentof a trailer (e.g., a target position for a steering cylinder, a targetposition of a trailer wheel, a target position of the entire trailer).The target position is a position of the component that allows thetrailer to follow the path of the tractor during travel, according toone embodiment.

Referring next to the schematic diagram shown in FIGS. 13A-13F, atrailer steering system 200 and a snow removal system 220 may operatevarious components of a trailer. In one embodiment, trailer steeringsystem 200 and snow removal system 220 are hydraulic systems, and thediagrams shown in FIGS. 13A-13F are hydraulic diagrams. In otherembodiments, at least one of trailer steering system 200 and snowremoval system 220 is another type of system (e.g., a pneumatic system,an electrical system, etc.).

As shown schematically in FIGS. 13A-13F, trailer steering system 200includes steering cylinder 132. In one embodiment, steering cylinder 132engages a steering arm to steer at least one wheel of the trailer. Asshown in FIGS. 13A-13F, steering cylinder 132 is coupled to a trailersteering manifold 202. Trailer steering manifold 202 is a hydraulicmanifold configured to regulate fluid flow between the actuators (e.g.,steering cylinder 132) and the pumps of the hydraulic system of thevehicle. According to the embodiment shown in FIGS. 13A-13F, trailersteering manifold 202 includes a valve 208 for affecting pressure insteering cylinder 132. In one embodiment, valve 208 includes anelectronic solenoid valve coupled to a movable valve gate such thatvalve 208 is electronically adjustable. A variable output from asteering control system may be provided to valve 208. In one embodiment,movement of the valve gate provides differing levels (e.g., flow rates,pressures, etc.) of fluid to steering cylinder 132, thereby changing theposition of steering cylinder 132 or the force applied by steeringcylinder 132.

Referring still to FIGS. 13A-13F, trailer steering system 200 furtherincludes an engine 204 coupled to a pump 205. As shown in FIGS. 13A-13F,pump 205 is a hydraulic pump. In other embodiments, pump 205 is apneumatic pump or another type of device. In one embodiment, engine 204rotates pump 205 to provide pressurized fluid to other components oftrailer steering system 200 and snow removal system 220. By way ofexample, engine 204 may be a diesel combustion engine. By way of anotherexample, pump 205 may be powered by an electric motor.

Trailer steering system 200 further includes a tank, shown as hydraulicreservoir 206. In other embodiments, the tank is a pneumatic tank or avessel configured to store another working fluid. Hydraulic reservoir206 holds excess hydraulic fluid resulting from changes in the extensionor contraction of steering cylinder 132 and other changes in trailersteering system 200 and snow removal system 220.

As shown schematically in FIGS. 13A-13F, snow removal system 220includes a plurality of actuators associated with the broom and blowersof a snow removal vehicle. According to the embodiment shown in FIGS.13A-13F, snow removal system 220 includes hitch height adjustmentactuators 222, broom swing actuators 224, broom lift actuators 226, snowshed actuators 228, snow deflect actuators 230, blower extend actuators232, and blower deflector actuators 234. In one embodiment, at least oneof hitch height adjustment actuators 222, broom swing actuators 224,broom lift actuators 226, snow shed actuators 228, snow deflectactuators 230, blower extend actuators 232, and blower deflectoractuators 234 are hydraulic cylinders. As shown in FIGS. 13A-13F, eachof hitch height adjustment actuators 222, broom swing actuators 224,broom lift actuators 226, snow shed actuators 228, snow deflectactuators 230, blower extend actuators 232, and blower deflectoractuators 234 are hydraulic cylinders. In other embodiments, at leastone of hitch height adjustment actuators 222, broom swing actuators 224,broom lift actuators 226, snow shed actuators 228, snow deflectactuators 230, blower extend actuators 232, and blower deflectoractuators 234 is another type of actuator (e.g., an electric actuator, apneumatic actuator, etc.).

The actuators of snow removal system 220 are positioned to engage acomponent of a snow removal vehicle (e.g., a broom, a blower, etc.) tofacilitate the performance of a snow removal function (e.g., adjust theposition of the broom, etc.). In one embodiment, the actuators areelectronically controlled (e.g., electronically actuated, coupled to anelectronically controlled valve, etc.). Such electronically controlledactuators may be operated based on user input or operated as part of abroom and blower control scheme. As shown in FIGS. 13A-13F, snow removalsystem 220 includes a plurality of actuator pairs positioned to performvarious snow removal functions. In other embodiments, snow removalsystem 220 includes a single actuator positioned to perform a snowremoval function. In still other embodiments, snow removal system 220includes more than two actuators positioned to perform a snow removalfunction.

As shown in FIGS. 13A-13F, circuitry, shown as hydraulic circuitry 250,couples snow removal system 220 with trailer steering system 200. In oneembodiment, hydraulic circuitry 250 facilitates the transmission ofpressurized hydraulic fluid from pump 205 to the actuators of snowremoval system 220. According to the embodiment shown in FIGS. 13A-13F,hydraulic circuitry 250 is local to snow removal system 220. In otherembodiments, various control circuitry for at least one of a broom and ablower may be located remotely from snow removal system 220. Hydrauliccircuitry 250 may be coupled to other subsystems of a snow removalvehicle.

Referring still to FIGS. 13A-13F, snow removal system 220 includes hitchheight adjustment actuators 222, broom swing actuators 224, broom liftactuators 226, snow shed actuators 228, snow deflect actuators 230,blower extend actuators 232, and blower deflector actuators 234. Hitchheight adjustment actuators 222 are configured to level a trailerrelative to a ground surface (e.g., front-to-back level, etc.),according to one embodiment. When actuated, broom swing actuators 224may adjust the deployed angle of the broom (e.g., the angle of the broomrelative to the snow removal vehicle, the angle of the broom relative tothe ground surface, etc.). Broom lift actuators 226 are positioned tovary the height of the broom relative to the ground surface. In oneembodiment, broom lift actuators 226 may raise or lower the position ofthe broom without adjusting the position of the frame of the trailer.Snow shed actuators 228 and snow deflect actuators 230 are positioned tofacilitate the deflection or removal of snow and other debris away frombroom 108 and trailer 104 by raising or lowering a shed, deflector, orother apparatus coupled to at least one of the broom and the trailer,according to one embodiment. In other embodiments, snow removal system220 includes more or fewer actuators positioned to perform various snowremoval functions.

According to one embodiment, a snow removal vehicle includes a blowerpositioned to produce an air stream that directs snow and other debrisfrom the broomed surface. Snow removal system 220 includes blower extendactuators 232 and blower deflector actuators 234 to facilitate theoperation of the blower. Blower extend actuators 232 may be coupled tothe blower and configured to vary the position thereof (e.g., byextending the blower laterally outward from the trailer, by extendingthe blower closer to the broom, etc.). Blower deflector actuators 234may be coupled to a blower deflector and configured to vary the positionthereof. By way of example, the blower deflector may facilitate theremoval of debris and snow by directing the stream of air produced bythe blower.

Referring next to the block diagrams shown in FIGS. 14-15, a steeringcontrol system 300 is used to control the steering of a pair of tractiveelements of a trailer (e.g., trailer 104). Steering control system 300may be implemented to steer one or more axles of a trailer. As shown inFIG. 14, steering control system 300 interacts with various othercomponents of a vehicle (e.g., snow removal vehicle 100) to control atrailer (e.g., trailer 104). Steering control system 300 may be acontroller configured to generate a control strategy for trailer 104.The control strategy may include one or more settings related to atleast one of steering cylinder 132 and locking cylinder 144. In oneembodiment, the control strategy includes adjusting the position of oneor more actuators, thereby selectively locking and adjusting theposition of the wheels. By adjusting the position of the wheels, thetrailer may be controllably steered into a different position. By way ofexample, a control strategy may include settings that center the wheelsof trailer 104, preventing the wheels from additively steering trailer104. By way of another example, a control strategy may include settingsthat steer the wheels of trailer 104 in the same direction as the wheelsof tractor 102. By way of still another example, a control strategy mayinclude settings that steer the wheels of trailer 104 in an opposingdirection relative to the wheels of tractor 102.

Trailer steering manifold 202 receives an input relating to the controlstrategy from steering control system 300 via an input/output (I/O)module 302. The control strategy may indicate to trailer steeringmanifold 202 a desired actuation of steering cylinder 132 (e.g.,extension, refraction, etc.). In one embodiment, valve 208 is actuatedto control the position of steering cylinder 132. I/O module 302 may beconfigured to receive input from steering control system 300 and toprovide the input to trailer steering manifold 202.

In the embodiment shown in FIG. 14, a valve 148 (e.g., a high-flowelectric solenoid valve having a quick-release feature, etc.) is coupledto I/O module 302 and locking cylinder 144. By way of example, valve 148may be electrically coupled to I/O module 302 (e.g., with an analogconnection, with a J1939 databus connection, etc.). In otherembodiments, valve 148 includes a solenoid valve, and a quick releasevalve is disposed between valve 148 and locking cylinder 144. Valve 148may be in fluid communication with locking cylinder 144. In oneembodiment, valve 148 is disposed between locking cylinder 144 and apressurized fluid source (e.g., a pressurized reservoir, a pump, etc.).Opening valve 148 may expose locking cylinder 144 to a pressurized fluid(e.g., a pressurized liquid, a pressurized gas, etc.). In oneembodiment, locking cylinder 144 retracts the locking pin when exposedto the pressurized fluid, thereby allowing rotation of the wheels (e.g.,to steer). In another embodiment, locking cylinder 144 extends thelocking pin when exposed to the pressurized fluid, thereby securing theposition of the wheels (e.g., in a straight-ahead orientation). Valve148 may be a solenoid valve or another type of valve that may beelectronically controlled through signals sent and received by I/Omodule 302.

Referring still to FIG. 14, sensor 136 may provide a sensor input tosteering control system 300. By way of example, the sensor input mayrelate to the position of steering cylinder 132. In one embodiment,sensor 136 is integrated as part of steering cylinder 132. In otherembodiments, sensor 136 is otherwise positioned. In still otherembodiments, a sensor (e.g., a linear position sensor, a rotationalposition sensor, etc.) is configured to provide sensor signals relatingto another steering component (e.g., the angular position of a hub, aposition of a steering arm, etc.). Steering control system 300 may usethe sensor input to determine a current position of steering cylinder132 or another component of a trailer. The current position may be usedto help determine a control strategy for adjusting the position ofsteering cylinder 132.

Referring to FIG. 15, a block diagram of steering control system 300 isshown in greater detail. As described above, steering control system 300may be configured to generate a control strategy for steering a trailerof a snow removal vehicle. Steering control system 300 may generallyreceive various sensor inputs relating to the position of a steeringcylinder, the trailer, a transmission gear, and the vehicle speed, amongother characteristics. A control strategy may be generated based on thetransmission gear, vehicle speed of the snow removal vehicle, and otherfactors relating to the operation of the snow removal vehicle. In oneembodiment, the transmission is configured to provide a transmissionstate to a processing circuit (e.g., as a reverse signal along ahardwired connection to an input of steering control system 300, with aJ1939 databus connection, etc.). In one embodiment, the transmissionstate relates to at least one of a selected transmission gear and anobtained transmission gear. According to another embodiment, steeringcontrol system 300 receives various sensor inputs relating to thedirection of travel of a vehicle (e.g., a tractor, a trailer, etc.). Inone embodiment, the system includes a sensor (e.g., an anti-lock brakesensor, etc.) that provides the sensor inputs to steering control system300. In other embodiments, steering control system 300 receives variousother signals relating to the direction of travel of the vehicle (e.g.,signals from a global positioning system, etc.). A control strategy maybe generated based on the direction of travel of the vehicle. By way ofexample, a processing circuit may be configured to control the steeringof a pair of tractive elements (e.g., tractive elements coupled to thechassis of a trailer, etc.) according to a control strategy that variesbased on the direction of travel of the vehicle. In one embodiment, thecontrol strategy includes centering the pair of tractive elements tofacilitate maneuvering the trailer when vehicle is traveling in areverse direction.

Steering control system 300 includes a processing circuit 304 includinga processor 306 and memory 308. Processor 306 may be implemented as ageneral purpose processor, an application specific integrated circuit(ASIC), one or more field programmable gate arrays (FPGAs), a group ofprocessing components, or other suitable electronic processingcomponents. Memory 308 is one or more devices (e.g., RAM, ROM, flashmemory, hard disk storage, etc.) for storing data and/or computer codefor completing and/or facilitating the various user or client processes,layers, and modules described in the present disclosure. Memory 308 maybe or include volatile memory or non-volatile memory. Memory 308 mayinclude database components, object code components, script components,or any other type of information structure for supporting the variousactivities and information structures of the present disclosure. Memory308 is communicably connected to processor 306 and includes computercode or instruction modules for executing one or more processesdescribed herein.

Memory 308 may include one or more modules configured to handle theactivities described in the present disclosure (e.g., the processes ofFIGS. 16-17). Memory 308 is shown to include a system information module310. System information module 310 may receive and store informationrelated to vehicle operation. The information may then be used by othermodules for determining various settings. For example, the informationmay include a sensor input received from sensor 136. The information mayfurther include a sensor input received from hitch angle sensor 150.Such information may be used to determine a target position of asteering cylinder, the wheels of a trailer, or the entire trailer. Theinformation may further include a transmission gear 342 (e.g., reversegear, first gear, second gear, etc.) of the vehicle as received from avehicle subsystem 340. Transmission gear 342 is an “obtained”transmission gear, according to one embodiment. Such information may beused to determine if the trailer needs to be steered and in whichdirection. The information may further include a current vehicle speed344 as received from a vehicle subsystem 340. The current vehicle speedmay be used to determine if the trailer can be steered safely. Theinformation may further include a current alignment of the tractor ofthe snow removal vehicle. The current alignment of the tractor may beused to align the trailer when the snow removal vehicle is in a forwardgear (e.g., such that the trailer appropriately tracks the vehicle).System information module 310 may further store historical information,trailer configuration information, or any other information that may beused by steering control system 300 to determine a control strategy tosteer the trailer.

Memory 308 further includes a trailer position module 312. Trailerposition module 312 may determine at least one of a current position ofa steering cylinder, a current position of the wheels of a trailer, anda current position of the trailer based on a sensor input from sensor136, a sensor input from hitch angle sensor 150, and other information.Sensor 136 may be embedded into steering cylinder 132 as described aboveand may provide sensor signals relating to a position of steeringcylinder 132. Trailer position module 312 may use the position ofsteering cylinder 132 relative to the other parts of the trailer toevaluate the current position of trailer 104 itself. In otherembodiments, trailer position module 312 determines the current positionof the trailer based on sensor input from only hitch angle sensor 150.

Memory 308 further includes a target position module 314. Targetposition module 314 may determine at least one of a target position of asteering cylinder, a target position of the wheels of a trailer, and atarget position of the trailer based on a sensor input from sensor 136,a sensor input from hitch angle sensor 150, and other information. Inone embodiment, the target position is calculated using informationregarding the physical characteristics of the trailer. In anotherembodiment, an operator may manually enter an override parameter (e.g.,a steering angle, etc.) that is added to or subtracted from thecalculated target position to produce a modified target position. Thetarget position may relate to a selected gear for the tractor of thesnow removal vehicle. For example, if the snow removal vehicle is in aforward gear, the target position may be a position that varies based onthe position of at least the position of a steering cylinder, the hitchangle, and the position of the wheels of the tractor. By way of anotherexample, if the snow removal vehicle is in a reverse gear, the targetposition may be a position that centers the wheels of the trailer. Hitchangle sensor 150 may be directly coupled to the hitch of the trailer,according to one embodiment, and measure the angle of the hitch relativeto the tractor or trailer. The hitch angle indicates a difference in howtractor 102 and trailer 104 are aligned. The hitch angle may be used bytarget position module 314 to steer the wheels of the trailer so thatthe hitch angle between the tractor and trailer is reduced or approachesa target value.

Memory 308 further includes a control strategy module 316. Controlstrategy module 316 is configured to use the current position of thesteering cylinder and the target position of the steering cylinder todetermine a control strategy for the trailer. The control strategy mayrelate to a position of one or more actuators for controlling theposition of the wheels of the trailer. The control strategy may indicatea level of actuation of, for example, steering cylinder 132 and lockingcylinder 144. The control strategy may be provided to I/O module 302(shown in FIG. 14) via an I/O interface 326. The control strategy outputmay be a variable output for engaging the actuators (e.g., the variableoutput may be related to a variable voltage used to control anelectrically-actuated solenoid valve).

In one embodiment, the variable output is adjusted based on vehiclespeed. For example, if a snow removal vehicle is traveling at a speedgreater than a threshold speed (e.g., 20 miles per hour), the variableoutput may be adjusted such that the rate of steering the axle andwheels of the trailer is reduced to avoid instability. As anotherexample, if the snow removal vehicle is traveling at a lower thresholdspeed while turning, the variable output may be adjusted to reduce therate of steering.

Control strategy module 316 may receive a current steering mode of thesnow removal vehicle (e.g., from steering mode module 318) thatindicates a desired operation of the vehicle, which may be used todetermine the control strategy. Control strategy module 316 may receivethe current transmission gear of the vehicle and determine the controlstrategy. If the vehicle is in a reverse gear, control strategy module316 may set a target position (e.g., a target position for steeringcylinder 132) that centers the wheels. If the vehicle is in a forwardgear, control strategy module 316 may set a target position that steersthe trailer according to a coordinated steering strategy. The actualtransmission gear may be provided by the transmission. In otherembodiments, the actual transmission gear is otherwise obtained.Utilizing the actual transmission gear reduces the risk of entering aninappropriate control strategy due to inadvertent selection of atransmission gear by an operator. In still other embodiments, controlstrategy module 316 utilizes another characteristic of the vehicle todetermine the control strategy (e.g., a selected transmission gear, arotation direction of the wheels of the tractor or trailer, etc.).

In one embodiment, control strategy module 316 may be configured toprovide a control strategy that locks the axle and wheels of the trailerin place once the wheels have been steered into a proper position (e.g.,a straight-ahead orientation). Control strategy module 316 may beconfigured to determine a position of locking cylinder 144 of lockingmechanism 140, for example, and engage locking mechanism 140 to securethe wheels (e.g., in a straight-ahead orientation) with a locking pin.

Memory 308 further includes steering mode module 318. Steering modemodule 318 may determine a steering mode that indicates one or moresettings to be used by control strategy module 316 for steering thetrailer. The steering mode may indicate how (or if) the trailer shouldbe steered. For example, the steering system of the snow removal vehiclemay be turned “off,” where the wheels of the trailer are not steered tomatch the path of the vehicle (e.g., the wheels are centered andlocked). By way of another example, the steering system of the snowremoval vehicle may be turned “on” and the steering system may be in oneof a “front mode” and a “coordinated mode.” In some embodiments, turningon or off the entire trailer steering system may require supervisorapproval (e.g., with a password, etc.), whereas a driver may be allowedto toggle between front mode and coordinated mode during ordinaryoperation of the vehicle. With the steering system turned “on” and withthe trailer steering system in the front mode, the trailer wheels arenot steered. With the steering system turned on and with the trailersteering system in the coordinated mode, the trailer wheels may beunlocked and steered such that the trailer path matches the path of thetractor. Regardless of the selected mode, the trailer wheels may becentered once the tractor is in reverse (e.g., once a reversetransmission gear is obtained, once the tractor or trailer begins tomove backward, etc.). Such a control scheme facilitates backing thetrailer as a driver may rely upon prior experience backing uptraditional, fixed-axle trailers.

In one embodiment, the steering mode may be determined by steering modemodule 318 based on input from vehicle subsystems 340, such astransmission gear 342. For example, the steering mode may beautomatically set to “front” when the snow removal vehicle is in areverse transmission gear 342 and “coordinated” when the snow removalvehicle is in a forward transmission gear 342. An operator (e.g., thedriver) of the snow removal vehicle may override the steering mode atany time using an interface (e.g., the interface of FIGS. 18-20). Inanother embodiment, the steering mode may not be automaticallydetermined, and an operator may manually set the steering mode at his orher discretion.

In one embodiment, steering mode module 318 may store configurationinformation for one or more operators (e.g., a driver, an administratoror manager, etc.) of the snow removal vehicle. Steering mode module 318may then set a steering mode based on the configuration information inaddition to vehicle subsystem 340 information. By way of example, thesystem may require that a manager set a desired steering mode for thesnow removal vehicle while the truck is in operation, instead ofallowing the driver of the truck to override the steering mode. By wayof another example, a driver may have desired steering mode settingsthat override default settings. In one embodiment, an operator mayprovide a password or other identification to steering control system300 (e.g., a user ID, a timekeeper code, etc.). Steering mode module 318or another module of steering control system 300 may verify theidentification prior to changing a steering mode of the snow removalvehicle. Such identification and authentication reduces the risk that aless experienced driver may improperly operate the vehicle.

Memory 308 further includes calibration module 320. Calibration module320 may be configured to calibrate at least one of sensor 136 and hitchangle sensor 150. In other embodiments, calibration module 320 receivesa user input to calibrate at least one of sensor 136 and hitch anglesensor 150. Calibration module 320 may prompt an operator of the snowremoval vehicle to drive forward or in a predetermined direction inorder to calibrate the sensors. For example, calibration module 320 mayprompt the operator to pull ahead and provide an indication tocalibration module 320 (e.g., that the vehicle has been pulled ahead)before calibrating hitch angle sensor 150.

Memory 308 further includes a graphical user interface (GUI) module 322.GUI module 322 is configured to generate a GUI for an operator of thesnow removal vehicle, such as the user interfaces shown in FIGS. 18-20,and to receive and interpret the user input from the user interface. Forexample, GUI module 322 may receive a user input relating to a change inthe steering mode, a change between automatic and manual steering of thetrailer, or otherwise. Steering control system 300 is further shown toinclude UI elements 330 and a display module 332 configured to providethe display to the user. UI elements 330 may allow the user to provide auser input via a touchscreen display, via a keyboard, a mouse or otherpointer, and/or via one or more buttons, knobs, or switches located onthe user interface or elsewhere in the snow removal truck, or otherwise.Display module 332 may be configured to provide a display as generallyshown in FIGS. 18-20.

Steering control system 300 further includes a sensor interface 324configured to receive data from sensor 136 and hitch angle sensor 150.Steering control system 300 also includes an interface 328 configured toreceive data from one or more vehicle subsystems 340 as described above.Still other interfaces may be included to facilitate the transmission ofsignals between the various components of steering control system 300.

Referring next to FIG. 16, a flow chart of a process 400 for controllingthe steering of the wheels of a trailer is shown, according to anexemplary embodiment. Process 400 may be executed by, for example,control strategy module 316 or another module configured to steer thewheels of a trailer. It should be understood that process 400 mayinclude various sub-steps. In other embodiments, process 400 includesmore or fewer steps than those shown in FIG. 16.

Process 400 includes calibration of the steering system (step 402). Forexample, step 402 may include calibrating at least one of a positionsensor (e.g., a linear position sensor coupled to a steering cylinder)and a hitch angle sensor of the trailer. Step 402 may be executed priorto operation of the snow removal vehicle (e.g., prior to plowing snow).Process 400 further includes a steering step (step 404). At step 404,the trailer steering may be turned on or off. In other embodiments, thetrailer steering may be turned on or off prior to step 404, and step 404may involve verification that the trailer steering is turned on.

Process 400 further includes determining if the steering mode iscurrently in a “front” mode (step 406). The front mode may correspond toa mode where the wheels and axle of the trailer are not steered to matchthe path of the tractor (e.g., the wheels and axle may be centered andlocked). If the steering mode is the front mode, process 400 includescentering and locking the rear axle of the trailer (step 408).

If the steering mode is not in front mode, process 400 includesdetermining if a tractor reverse gear is obtained (step 410). In otherwords, at step 410, process 400 may check if the snow removal vehiclehas been switched into a reverse gear. In one embodiment, thetransmission gear of the snow removal vehicle may be obtained based on acurrent status of the transmission gear. In another embodiment, the gearselected by an operator may be used at step 410. The use of the currentstatus of the transmission gear instead of the selected gear may reducethe risk of using the reverse gear in scenarios where the operator hasinadvertently selected the reverse gear.

If the tractor is not in a reverse gear, then the current steering modeof the snow removal vehicle may continue. The trailer may be steeredbased on sensor input from a hitch angle sensor and other sensor input(step 412). In one embodiment, step 412 includes evaluating a feature(e.g., a position, a configuration, etc.) of a locking cylinder. Step412 may include actuating a locking cylinder to unlock the wheels. Byway of example, such actuation may include sending a command signal toopen a pneumatic valve or engage a pump such that pressurized fluidovercomes a biasing spring and disengages a locking pin from a lockingplate. If the tractor is in a reverse gear, process 400 includesdetermining if an auto-center mode is selected (step 414). An operatormay choose to select or de-select an auto-center mode. The auto-centermode may automatically center the wheels of the trailer whenever thesnow removal vehicle is in a reverse gear, without input. If theauto-center mode is selected by the operator, the axle and wheels of thetrailer are steered into a centered position (step 416) and process 400may continue to monitor the current transmission gear. If theauto-center mode is not selected by the operator, the snow removalvehicle may continue to be steered based on the current steering mode atstep 412. In one embodiment, step 416 includes locking the wheels bysending a command signal to open a relief valve (e.g., a quick-releasevalve, etc.) such that a biasing spring engages a locking pin with alocking plate.

Referring next to FIG. 17, a flow chart of a process 500 for locking andunlocking the axle and wheels of a trailer for a vehicle (e.g., a snowremoval vehicle) is shown, according to an exemplary embodiment. Process500 may be executed by, for example, control strategy module 316 oranother module configured to steer the wheels of a trailer. It should beunderstood that process 500 may include various sub-steps. In otherembodiments, process 500 includes more or fewer steps than those shownin FIG. 17.

Process 500 includes a calibration of the steering system (step 502).For example, step 502 may include calibrating at least one of a positionsensor (e.g., a linear position sensor coupled to a steering cylinder)and a hitch angle sensor of the trailer. Step 502 may be executed priorto operation of the snow removal vehicle (e.g., prior to plowing snow).Process 500 further includes a selection of an “off” steering mode (step504). At step 504, the steering mode of the trailer is set to off andinterlocks are met (e.g., the axle and wheels are in proper position).

Process 500 further includes determining if the axle is centered (step506). Step 506 may include the evaluation of sensor signals from asensor (e.g., linear position sensor) associated with a steeringcylinder or the position of the wheels. By way of example, step 506 mayinclude the evaluation of sensor signals from a linear position sensorthat is integrated as part of a steering cylinder. If the wheels are notcentered, the wheels may be centered (step 508) by sending a controlsignal to an actuator. Process 500 further includes changing thesteering mode of the snow removal vehicle to “off” and locking the axleand wheels (step 510), completing the axle locking process.

Process 500 later includes determining if an operator has activated thesteering system (step 512). The activation of the steering system may bemade by an operator via a user interface as generally described in FIGS.18-20. The steering system may be initiated by an operator preparing tooperate a snow removal vehicle, for example. If the operator has notactivated the steering system, the axle and wheels may remain locked(step 514). If the operator has activated the steering system, process500 includes determining if the selected steering mode is the “front”mode (step 516). If the front mode is selected, the axle and wheelsremain locked (step 514), as the steering mode indicates that thetrailer should be steered based on the current position of the axle andwheels. If a different steering mode is selected by the operator or bysteering control system 300, the axle and wheels are unlocked (step518).

Referring generally to FIGS. 18-20, various user interfaces that anoperator may use to interact with the steering control system of thepresent disclosure are shown, according to exemplary embodiments.Referring to FIG. 18, a user interface 600 is illustrated. Userinterface 600 may be located on, for example, the dashboard of a vehicle(e.g., snow removal vehicle 100), within reach of the driver, operator,or other occupant of the vehicle. In other embodiments, user interface600 may be located in another area of the vehicle, or additional userinterfaces may be provided. For example, one or more buttons, switches,or levers may be located on an arm rest or other vehicle feature withinreach of the operator. The operator may control some or all aspects ofthe steering control process via the user interface.

User interface 600 includes general vehicle information, such as avehicle speed, fuel level, system diagnostics, etc. User interface 600may further include one or more warning lights related to generalvehicle operation. User interface 600 may further include snow blower orsnow plow statuses. For example, if the snow blower is currently in use,one or more indicators related to snow plow or snow blower functionalitymay be provided. Similarly, user interface 600 may further includetrailer broom properties (e.g., broom wear, broom speed, broom RPM,etc.). User interface 600 may indicate if the trailer steering system isin a coordinated mode via indication 602 or if the axle of the traileris locked in position via indication 604. User interface 600 may includean indication 606 for an on/off status of the trailer steering system.As shown in FIG. 18, user interface 600 indicates that the trailersteering system is off.

User interface 600 may include various options that an operator mayselect to bring up another screen. For example, the user may viewvehicle gauge information, broom settings, maintenance information, ordiagnostic information of the vehicle. In one embodiment, the operatormay select the “broom settings” option 608 to bring up user interface610 shown in FIG. 19. User interface 610 may display various broomsettings that the operator may view or adjust. Via user interface 610,the operator may adjust a broom pattern (e.g., rotation and position ofthe broom).

Via user interface 610, the operator may also adjust one or moresettings related to the steering of the trailer, as the broom is coupledto the trailer and trailer adjustments may impact the performance of thebroom. For example, user interface 610 indicates a hitch sensor deadband612 that indicates the deadband of the hitch angle sensor, a hitch/axleturning ratio 614 that indicates the ratio between the steering wheel ofthe snow removal vehicle and the wheels of the trailer, and a steeringoffset angle 616 as a manual override to the target position calculatedby the steering control system (e.g., an angular value relating to thesteering angle of the trailer wheels, an angular value relating to theangle of the trailer relative to the tractor, etc.). In one embodiment,user interface 610 facilitates user manipulation of at least one ofhitch sensor deadband 612, hitch/axle turning ratio 614, and steeringoffset angle 616.

Referring now to FIG. 20, upon a user selection to change one or moresettings related to the steering control system of the vehicle, userinterface 620 may be presented to the operator. User interface 620 mayinclude a plurality of options related to the steering control system.For example, an operator may choose to activate or deactivate a “smarttrack system” at option 622 (i.e. the steering control system may beturned on or off). The operator may further choose the type of steeringmode at option 624. For example, the operator may choose to put thetrailer in a coordinated steering mode such that the wheels of thetrailer are steered. By way of another example, the operator may chooseto put the trailer in a front steering mode, where the wheels of thetrailer are not steered. The operator may further choose whether or notto have the wheels of the trailer auto-centered when the snow removalvehicle is in a reverse transmission gear at option 626. The operatormay further choose to calibrate the sensors (e.g., hitch angle sensorand linear position sensor) at option 628. In still other embodiments,user interface 620 may allow an operator to manually set the steeringangle for the trailer wheels, set the hitch angle, or set still anotherfeature of the steering control system (i.e. the trailer steering systemmay be operated in a manual mode).

User interface 620 may additionally display axle and wheel properties.For example, an axle position 630 and hitch position 632 is displayedthat illustrates the current position of the axle and hitch (e.g., as araw count, as a measured or computed angle, etc.). An axle lock status634 may also be displayed that indicates whether the axle and wheels ofthe trailer are locked or free to turn. User interface 620 may furtherillustrate the requested and actual statuses for the steering controlsystem, thereby reducing the risk that an operator may assume the systemhas responded before the requested action has occurred.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, the position of elements may bereversed or otherwise varied and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure. The order or sequence of any process or method stepsmay be varied or re-sequenced according to alternative embodiments.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions and arrangement of the exemplaryembodiments without departing from the scope of the present disclosure.

The present disclosure contemplates methods, systems, and programproducts on any machine-readable media for accomplishing variousoperations. The embodiments of the present disclosure may be implementedusing existing computer processors, or by a special purpose computerprocessor for an appropriate system, incorporated for this or anotherpurpose, or by a hardwired system. Embodiments within the scope of thepresent disclosure include program products comprising machine-readablemedia for carrying or having machine-executable instructions or datastructures stored thereon. Such machine-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer or other machine with a processor. By way of example,such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to carry or storedesired program code in the form of machine-executable instructions ordata structures and which can be accessed by a general purpose orspecial purpose computer or other machine with a processor. Combinationsof the above are also included within the scope of machine-readablemedia. Machine-executable instructions include, for example,instructions and data, which cause a general purpose computer, specialpurpose computer, or special purpose processing machines to perform acertain function or group of functions.

Although the figures may show a specific order of method steps, theorder of the steps may differ from what is depicted. Also two or moresteps may be performed concurrently or with partial concurrence. Suchvariation will depend on the software and hardware systems chosen and ondesigner choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps and decision steps.

What is claimed is:
 1. A trailer, comprising: a chassis having a hitch;an axle having a tractive element rotatably coupled to the chassis; andan actuator coupled to the chassis and positioned to steer the tractiveelement in response to an input, the input varying based on at least oneof a speed, a transmission gear, and a steering mode of a tractorvehicle.
 2. The trailer of claim 1, wherein the input relates tocentering the tractive element to facilitate maneuvering the trailer. 3.The trailer of claim 1, wherein the input relates to steering thetractive element such that the trailer follows the tractor vehicle. 4.The trailer of claim 1, further comprising a first sensor positioned toindicate a position of the actuator.
 5. The trailer of claim 4, furthercomprising a second sensor positioned to indicate an angle of thetrailer relative to the tractor vehicle.
 6. The trailer of claim 4,wherein the actuator includes a hydraulic cylinder and the first sensorincludes a linear position sensor.
 7. The trailer of claim 1, furthercomprising a locking mechanism coupled to the chassis and configured toselectively secure the tractive element.
 8. The trailer of claim 7,wherein the locking mechanism includes a locking pin moveably coupled tothe chassis with a locking actuator.
 9. The trailer of claim 8, whereinthe locking actuator includes an air-released spring.
 10. A steeringcontrol system for a trailer, comprising: an axle having a tractiveelement rotatably coupled to a chassis; an actuator positioned to steerthe tractive element; and a processing circuit configured to: evaluateat least one of a speed, a transmission gear, and a steering mode of atractor vehicle; and engage the actuator to steer the tractive elementaccording to a control strategy that varies based on at least one of thespeed, the transmission gear, and the steering mode of the tractorvehicle.
 11. The steering control system of claim 10, wherein theprocessing circuit is configured to receive a first sensor input from afirst sensor, and wherein the processing circuit is configured todetermine a current position of the actuator based on the first sensorinput.
 12. The steering control system of claim 11, wherein theprocessing circuit is configured to receive a second sensor input from asecond sensor, and wherein the processing circuit is configured todetermine a target position for the actuator based on the second sensorinput.
 13. The steering control system of claim 12, wherein theprocessing circuit is configured to steer the tractive element based onthe target position and the current position of the actuator.
 14. Thesteering control system of claim 10, wherein the processing circuit isconfigured to engage the actuator to center the tractive element inresponse to at least one of the speed of the tractor vehicle exceeding athreshold speed, the transmission gear being a reverse gear, and thesteering mode being a front steering mode of operation.
 15. The steeringcontrol system of claim 14, further comprising a locking mechanismcoupled to the chassis, wherein the processing circuit is configured toengage the locking mechanism, and wherein the processing circuit isconfigured to selectively secure the tractive element after centeringthe tractive element by engaging the locking mechanism.
 16. The steeringcontrol system of claim 15, further comprising a user input device,wherein the processing circuit is configured to receive a user inputfrom the user input device, the user input including a command to securethe axle, wherein the processing circuit is configured to center thetractive element and engage the locking mechanism in response to thecommand to secure the axle.
 17. The steering control system of claim 16,wherein the processing circuit is configured to engage the actuator tosteer the tractive element such that the trailer follows the tractorvehicle in response to at least one of the speed of the tractor vehiclebeing less than the threshold speed, the transmission gear being aforward gear, and the steering mode being a coordinated steering mode ofoperation.
 18. A method of steering a trailer comprising: identifying anoperating state of a tractor vehicle with a processing circuit; steeringa tractive element with an actuator when the operating state relates toa first mode of operation of the tractor vehicle; and centering thetractive element with the actuator when the operating state relates to asecond mode of operation of the tractor vehicle.
 19. The method of claim18, wherein the first mode of operation relates to at least one of aspeed of the tractor vehicle being less than a threshold speed, atransmission gear of the tractor vehicle being a forward gear, and asteering mode being a coordinated steering mode of operation; andwherein the second mode of operation relates to at least one of thespeed of the tractor vehicle exceeding the threshold speed, thetransmission gear of the tractor vehicle being a reverse gear, and thesteering mode being a front steering mode of operation.
 20. The methodof claim 18, further comprising: evaluating a first sensor input from aposition sensor and a second sensor input from a hitch angle sensor;determining a target position of the actuator with the processingcircuit based on the first sensor input and the second sensor input; andengaging the actuator based on the target position.